<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      width: 100px;
      height: 100px;
      background-color: deeppink;
    }
  </style>
</head>

<body>
  <div>1</div>
  <div>2</div>
  <div>3</div>

  <script>
    var divs = document.querySelectorAll('div');
    divs[0].onclick = function () {
      alert(111);
      // 1.传统方式删除事件
      divs[0].onclick = null;
    }
    // 2. removeEventListener 删除事件
    divs[1].addEventListener('click', fn); // 里面的fn，不需要调用加小括号
    function fn () {
      alert(222);
      divs[1].removeEventListener('click', fn);
    }

    // 3.
    divs[2].attachEvent('onclick', fn1);
    function fn1 () {
      alert(333);
      divs[2].detachEvent('onclick', fn1);
    }
  </script>
</body>

</html>